If over 50 get a 90 day non o visa before coming to Thailand, when you arrive open a bank account with Kasikornbank ASAP, then get an agent to sort out your 12 month extension, no border runs required just 90 day reporting that the agents will do for about 100 bht.
Then renew every year with agent, the agent will sort out the 800,000bht required for the extension.
With a mtv you will still need to leave every 60 days land border with Cambodia is shut so you will need to fly out to return or face a long bus ride to Loas.
you were lucky 3 visits and days of my life I will never get back,having to go to the branch I opened the account in miles away from where I live was a pain .